Preparation

Beat butter, powdered sugar, lemon peel and salt in large bowl until well blended. (Do not overmix.) Add 1/2 egg; beat until well blended. Stir in ground hazelnuts. Gradually stir in flour. Divide dough into fourths. Wrap each portion; refrigerate about 2 hours or until firm.

Preheat oven to 350°F. Line cookie sheets with parchment paper. Roll out dough, one fourth at a time, 1/8 to 1/16 inch thick on floured pastry cloth. Cut out with 1-1/4-inch round cookie cutter. Place 3/4 inch apart on prepared cookie sheets.

In small heavy saucepan over low heat, melt chocolate and shortening; stir until smooth. Press cookie layers lightly together. Dip top of each cookie into chocolate mixture just to cover. Shake to remove excess chocolate. Place cookies, chocolate side up, on wire racks; press reserved whole hazelnuts into soft chocolate in centers of cookies. Let stand until chocolate is set.